But shops say the system is misleading; a score of zero still allows a food business to operate and scores can change depending on seemingly small factors – including correctly completed paperwork – and on even on the person inspecting.

Some businesses have called on a pass-fail system to be implemented to ensure greater clarity for business owners and customers.

Sheron Jones, of Bridgend, runs a sandwich bar and a separate carvery business in Swansea.

The 59-year-old said that although she operates both her businesses in exactly the same way, one received a hygiene rating of five while the other was awarded a three.

Sheron said: “People looking at my three-star will think we’re not keeping it as clean. I think it’s very unfair.

“They could make the paperwork easier for businesses. I used to work in a bank so I know paperwork – and it’s not straightforward.”

Alan’s business was given a hygiene rating of one, but he was told by officials it would have been a four if he had completed some paper records correctly.

Alan claimed the rating awarded also changed depending on the person who inspected the premises.

He said: “On a previous visit, I had a complaint that there was blood on a door handle of the fridge.

“And then another person came in and said, ‘You’re a butcher’s shop – so you’re bound to have a bit of blood somewhere’.”

Niall McCormack, who owns Café 37 in Cathays, Cardiff, which received a hygiene rating of three, said: “I know hand on heart that we do a good job with cleanliness.

“We were marked down because a handwash dispenser in the staff toilets was empty. There were others there in the store room.

“It’s pot luck when they turn up because they turn up out of the blue. It’s just putting a blindfold on and throwing a dart. Somebody could score fabulously well because [the café] has been quiet the day before and they have got on top of the cleaning.”

A spokeswoman for the Federation of Small Businesses said: “Undoubtedly receiving low scores could be detrimental to small food operators in Wales. That is why we’ve called on the Welsh Government to issue strong guidance to food authorities and businesses to ensure that there’s adequate awareness of the impact of this legislation.

“We believe the Food Standards Agency should not only promote the scheme but highlight best practice in food hygiene to enable businesses to plan and aim for higher ratings.”

A Welsh Government spokeswoman said: “Food hygiene is essential for the protection of public health. The rating scheme will help drive up standards, so it will benefit both consumers and businesses alike.

“The scheme will enable consumers to make more informed choices about where they choose to eat or shop for food, while good food hygiene means a higher rating which is good for business.

“If the Bill becomes law, it is expected that the mandatory scheme will not come into operation until late 2013, allowing businesses to prepare.”